I have to politely disagree. The front & rear systems are really not connected hydraulicly. They have fluid between the front and rear pistons and when you brake the piston in the M/C pushes against the fluid pressure in between the pistons in the M/C. But if you loose pressure from a leak in either system the spring between the pistons in the M/C will compress if you loose fluid from a leak in that half and the spring will compress until it hits the piston and still applies the half brake system you still have. But the pedal will be lower because you lost the fluid between the pistons and the pedal drops when the spring compresses. Same if the other half looses fluid from a leak it will compress the front spring and still have the other half the brakes. Even on an old all drum system like on my car if you have the safety valve on the car the front and rear systems are still not hydraulicly connected. Each system has fluid pressure on one side of a piston in the safety valve to move it over with a pressure losss but they are not connected by hydraulic fluid. Ron